Yes, you can. You will get the full value of the GAD ($82.00) toward the $259 cost of the SP. Your monthly payment will be about $15.71 (including tax). The first monthly payment will be charged to your credit or debit card within one business day, and the other eleven payments at one month intervals.
If you go to the locked sticky Everything About WDW Tickets in this Forum, especially Post #21, you can get a lot more information. An easy way to get to the sticky is by clicking on the link in my signature.